1. Field of the Invention
The present invention relates to a relay connection circuit and a relay connector, in particular to a relay connection circuit and a relay connector with a reduced number of connection lines leading out from one side of the relay connector.
2. Description of the Related Art
In various kinds of machine tools, several sensors are installed around them which transmit certain signals to perform different modes of control operation.
In the case of the present invention, a plurality of power supply lines (hereinafter referred to as “Power Line”) and signal lines are connected between substrate connectors and sensors in a particular machine tool in order to supply electric power to the sensors. In recent years, the number of power lines and signal lines installed has increased as machine tools and the like have become multifunctional.
FIG. 12 shows a known connection circuit of power lines and signal lines between a machine tool and a plurality of sensors, wherein FIGS. 12(a) and (b) respectively show examples of two different connection circuits.
In the connection circuit 100A shown in FIG. 12(a), a substrate connector 102A provided in the machine tool consists of a plug-type connector 102a and a socket-type connector 102b, power lines 1031 to 1038 and signal lines 1041 to 1048 which are severally connected to the plug-type connector 102a, and the tips of the said power lines and signal lines are connected to a plurality of sensors (S1 to S8).
In this connection circuit, the 8 sensors S1 to S8, to which 2 power lines and 1 signal line are respectively connected, are in turn connected to the substrate connector 102A, and each of the plug-type connector 102a and the socket-type connector 102b of the substrate connector 102A requires 24 contacts. On the other hand, 16 power lines and 8 signal lines are required between sensors S1 to S8 and the plug-type connector 102a. 
There may be more than one signal line but if the number of sensors is increased, the number of signal lines will increase in proportion to the increase in the number of sensors, and in such an event the size of the substrate connector must be enlarged accordingly.
In the connection circuit 100B shown in FIG. 12(b), relay connectors 1051 to 1058 are provided between sensors S1 to S8 and a substrate connector 102B. The same number of power lines and signal lines as that of connection circuit 100A is required in this connection circuit.
Japanese Laid-Open Patent Publication No. 9-115626 (FIG. 7, left column on page 4) describes an electric circuit using branch connectors in which crossover wiring is disposed.
The electric circuit uses branch connectors where a flat plate branch conductor, in which a plurality of first and second tab contacts are severally formed on both sides of a strip-shaped common conductor part (crossover wiring) is disposed, and the power lines and a number of electric components are connected to the first tab contacts and the second tab contacts, respectively.
According to this electric circuit, electric power can be distributed from the power lines to several electric components via the common conductors.
However, because the known connection circuit utilizes a large number of power lines, the number of contacts of the substrate connector accordingly becomes larger, thereby requiring a large-sized connector. Considering that machine tools and the like have increasingly become smaller and multifunctional, such that several components and wirings connecting the components are intricately stretched, conceptualizing a design to provide space for mounting a large-sized connector has become difficult.
Even using the branch connectors described in Japanese Laid-Open Patent Publication No. 9-115626 cannot solve this problem. Because the branch connectors form a branch connection circuit by disposing the crossover wiring in a connector housing, a connection circuit of different connection lines, particularly power lines and signal lines, cannot be established.